Install xpad

 $ sudo apt install xpad

[sudo] password for dhwan: 

Reading package lists... Done

Building dependency tree       

Reading state information... Done

The following additional packages will be installed:

  libgtksourceview-3.0-1 libgtksourceview-3.0-common

The following NEW packages will be installed:

  libgtksourceview-3.0-1 libgtksourceview-3.0-common xpad

0 upgraded, 3 newly installed, 0 to remove and 17 not upgraded.

Need to get 596 kB of archives.

After this operation, 3.657 kB of additional disk space will be used.

Do you want to continue? [Y/n] y

Get:1 http://id.archive.ubuntu.com/ubuntu focal/universe amd64 libgtksourceview-3.0-common all 3.24.11-2 [276 kB]

Get:2 http://id.archive.ubuntu.com/ubuntu focal/universe amd64 libgtksourceview-3.0-1 amd64 3.24.11-2 [227 kB]

Get:3 http://id.archive.ubuntu.com/ubuntu focal/universe amd64 xpad amd64 5.4.0-1 [92,0 kB]

Fetched 596 kB in 5s (118 kB/s)

Selecting previously unselected package libgtksourceview-3.0-common.

(Reading database ... 314671 files and directories currently installed.)

Preparing to unpack .../libgtksourceview-3.0-common_3.24.11-2_all.deb ...

Unpacking libgtksourceview-3.0-common (3.24.11-2) ...

Selecting previously unselected package libgtksourceview-3.0-1:amd64.

Preparing to unpack .../libgtksourceview-3.0-1_3.24.11-2_amd64.deb ...

Unpacking libgtksourceview-3.0-1:amd64 (3.24.11-2) ...

Selecting previously unselected package xpad.

Preparing to unpack .../xpad_5.4.0-1_amd64.deb ...

Unpacking xpad (5.4.0-1) ...

Setting up libgtksourceview-3.0-common (3.24.11-2) ...

Setting up libgtksourceview-3.0-1:amd64 (3.24.11-2) ...

Setting up xpad (5.4.0-1) ...

Processing triggers for desktop-file-utils (0.24-1ubuntu3) ...

Processing triggers for mime-support (3.64ubuntu1) ...

Processing triggers for hicolor-icon-theme (0.17-2) ...

Processing triggers for gnome-menus (3.36.0-1ubuntu1) ...

Processing triggers for libc-bin (2.31-0ubuntu9.2) ...

Processing triggers for man-db (2.9.1-1) ...

Processing triggers for bamfdaemon (0.5.3+18.04.20180207.2-0ubuntu2) ...

Rebuilding /usr/share/applications/bamf-2.index...